1. Field of the Invention
This invention relates generally to a control architecture for a vehicle system and, more particularly, to a control architecture for a complex vehicle control system that is designed in a hierarchical manner from top to bottom.
2. Discussion of the Related Art
Modern vehicles are complex electrical and mechanical systems that include many different parts and sub-systems, such as actuators, sensors, controllers, communication buses, etc., that are integrated in a hierarchical configuration. The design and integration of these various devices and sub-systems is a complex process that requires many different components and modules to interact with each other in an efficient and reliable manner.
Conventional vehicle control systems, such as anti-lock brake system (ABS), traction control system (TCS), electronic stability control system (ESC), etc., are typically developed independently of each other and are incorporated into the vehicle one at a time to achieve their individual objectives. Such a design process often results in resource and objective conflicts and a functional overlap between different component features and sub-systems that requires arbitrated control. Further, arbitrated control often leads to performance trade-offs or even conflict. Also, such a design technique tends to be more hardware dependent and has a lack of coordination and sharing of resources. Further, conventional vehicle control systems are mainly for driver-commanded vehicle dynamics, including ride, handling and stability, and lack of the ability to handle driver assist and active safety features, and sensor-guided autonomous or semi-autonomous driving with environmental sensors.
As a result of the increasing number and complexity of vehicle components and sub-systems with multiple cross-functions, the functional overlap and interaction of the components become inevitable with multiple objectives ranging from enhanced safety, comfort and convenience to fuel economy for inter-vehicle and vehicle to environmental controls. Further, many smart and adaptive vehicle features are enabled by 360° sensing, and also, longitudinal, lateral and roll dynamic controls with multiple active chassis and powertrain actuators.
The above-described conventional vehicle control systems are designed in a bottom-up based design approach in which features are developed one at a time, and added to the over-all system one-by-one, which often leads to system complication, unmanageability and lack of optimization. These systems are mainly feedback based with trial and error approaches, and often limit their applications to near-limit or non-linear operating regions. Typically, they are hardware dependent, with feature-based design from end-to-end that often limits reusability among common functionalities, and flexibility for fault tolerance, electrical architecture and supplier sourcing. Arbitrated controls are typically applied among the features that often lead to potential conflict and performance trade off.
In the bottom-up design approach discussed above, it is necessary to validate the operation of the control system by first building the control system and then determining its operability by trial and error. Thus, as more elements are added to the control system, the ability to provide such validation becomes more complex and costly. Therefore, because each supplier develops their components independent of each other, the complexity of integrating the components becomes much more complex, and the ability to interchange one supplier's component with another becomes problematic. Further, such a design strategy causes a number of duplications.